Common fault in the valve repair solution

Maintenance personnel of the valve, the valve production process must have a basic valve repair knowledge, the conventional valve damage to timely maintenance and prevention, the following are some common valve troubleshooting approaches and methods of prevention

1, stuffing box leakage

Run, run, drip, the main aspects of leakage, we often see in the factory.

 A stuffing box leakage causes the following:

① filler and the erosion of media, temperature, pressure incompatible; ② The loading method differences error, circled the entire root filler into the most vulnerable to leakage; ③ stem machining accuracy or surface finish is not enough, or ellipticity or nicks; ④ The stem pitting, or rust due to lack of protection of the open air; ⑤ The stem bending; ⑥ The filling materials used for too long has been aging; ⑦ manipulation is too fierce.

Eliminating packing leakage is: (1) accurate selection of the filler; ② According to the accurate filling; ③ The stem cells processing differences, to repair or replace, surface finish, minimum ▽ 5, more important, to achieve more than ▽ 8, and no other defects; ④ to take protective measures to prevent corrosion, has been to replace the corroded; to ⑤ stem bending straightening or update; the ⑥ filling materials used by a certain time, to be replaced; ⑦ manipulation to pay attention to a smooth, slow to open slow off to prevent drastic changes in temperature or medium impact.

2, closed pieces of leakage

Usually the stuffing box leak is called leakage, called the closed parts within the vent. Closed leak, the valve inside, not easy to find.

Closed pieces of leakage can be divided into two categories: one is the sealing surface leakage, and the other seals roots leak.

Causes of leakage are: ① sealing surface grinding; ② ring with the valve seat, the valve with Qi Yan; ③ valve flap and valve stem is not strong *; (4) stem bending and torsion, so that the upper and lower closed pieces of differences error; ⑤ closed too fast, bad or has already damaged sealing surface contact; ⑥ The choice of materials properly, and withstood the erosion of live media; ⑦ globe valve, gate valve for regulating valve. Sealing surface to withstand the erosion of the live high-speed active medium; to ⑧ some media, the valve is closed gradually cooled, so that the sealing surface float to the surface of the slit will produce erosion phenomenon; to ⑨ some of the sealing surface and the valve seat, valve valve threaded connection between the easily produce the oxygen concentration cell, erosion loose; ⑩ welding slag, rust, dust and other impurities embedded in, or produced in the system blocking all mechanical parts off the spool, so that the valve can not be locked.

 

The precautionary approach:

 (1) prior to use necessary to really try to pressure leak testing and found that the sealing surface leakage or roots seals leak, properly handle before use; ② The advance check valve of the various components is intact, stem bending and torsion can not be used or the valves and valve stem connect the valve can not be *; (3) the valve off the critical steady strength, not to Meng Jin, such as bad or block hinder contact between the sealing surface, should immediately open a little, so that the debris outflow, and then carefully closed; ④ the selection of the valve, not only to consider the corrosion resistance of the body, but also to consider the closed parts of erosion resistance; ⑤ The structural characteristics in accordance with the valve, the use of accurate parts need to adjust the flow control valve; ⑥ The for off the cooling medium and large temperature difference between the situation after the valve in the cooling and then the valve is closed; ⑦ valve seats, valve and seal threaded connections, Teflon belt threaded between the filler, so that The exclusion does not idle; the ⑧ may fall into the valve of impurities, the filter should be added in front of the valve.

 

3, the valve stem down failure

Stem down failure reasons: to ① manipulate excessive thread injury; ② The lack of lubrication or lubricant failure; (3) stem bending and torsion; (4) surface finish is not enough; the ⑤ tolerances are not allowed to bite too tight; ⑥ stem nut tilt; ⑦ improper choice of materials, such as stem and stem nut for the unification of material, easily bite; ⑧ thread media erosion (refers to the dark bar valve or valve stem nut in the lower); the ⑨ open valve the lack of protection. stem threads are covered with dust and sand, or rain frost by corrosion.

 

Prevention methods:

(1) carefully manipulate closed when not to Meng Jin, and not open to the top dead center, open enough after the hand wheel to reverse a twice, so that the thread on the side of the seal in order to avoid the media to promote the stem upward impact; ② often check the lubrication to maintain a normal state of lubrication; ③ Do not use a long lever opening and closing valves, workers accustomed to using a short lever to strictly control the force measured, to prevent twisting bend the stem (refer to the hand wheel and stem directly connected to the valve); ④ The progress processing or repair quality to achieve regulatory requirements; to ⑤ material to be resistant to erosion, to adapt to temperature and other works on the premise; the ⑥ stem nuts not to use the same with the stem material; and the ⑦ plastic for stem nut, checking strength, can not consider only the good corrosion resistance and low coefficient of friction must also consider the strength of the subject, strong enough, do not use; ⑧ open valve and stem protection; ⑨ normally open valve, hand wheel to schedule rolling, so as not to stem rust to live

 

4, other

Valve gasket leak: The main reason is impatience erosion, not suited to working temperature and pressure; high temperature valve temperature. Methods of prevention: A washers compatible and works on the premise, the suitability of the new valve to check the gasket material, such as not suitable to be replaced. Temperature valve, when in use and then tight again bolt.

 

The valve body cracking: general freezing caused. Cold weather, the valve must have insulation with thermal measures, otherwise should be discontinued after valve and connecting pipe in the water row clean (if any valve bottom plugs, open wire blocking the drainage).

Hand wheel damage: impact or a long lever manipulation violently due. Handling staff and other relevant staff to pay attention, could have been prevented.

 

Valve packing gland rupture: compression packing force is not the average, or gland (usually cast iron) defect. Compression packing to symmetrically rotating screws, non-skew. Must not only pay attention to large and hub parts manufacture, but also pay attention to like sub-elements of the gland, or affect the use.

Connection of the stem and the valve plate failure: valve stem rectangular head and ram T-shaped slot connection in the form of more T-shaped slot is sometimes not processing, so to stem the rectangular head wear out sooner. Mainly from manufacturing to resolve. And use T-shaped slots make up processing, it has a certain finish.